package com.patterns.patterns06.singleton;

/**
 * Created by kobe on 2017/7/21.1:09
 * <br/>
 * Description:
 */
public class Singleton {

    /* 持有私有静态实例，防止被引用，此处赋值为null，目的是实现延迟加载 */
    private static Singleton instance = null;

    /* 私有构造方法，防止被实例化 */
    private Singleton() {
    }

    /* 静态工程方法，创建实例 */
    public static Singleton getInstance() {
        if (instance == null) {
            instance = new Singleton();
        }
        return instance;
    }

    /* 如果该对象被用于序列化，可以保证对象在序列化前后保持一致 */
    public Object readResolve() {
        return instance;
    }


    // 如果是在多线程环境下这个 getInstance() 方法可以，如下写。
    public static Singleton getInstance_1() {
        if (instance == null) {
            synchronized (instance) {
                if (instance == null) {
                    instance = new Singleton();
                }
            }
        }
        return instance;
    }

    private static class SingletonFactory{
        private static Singleton instance = new Singleton();
    }
    public static Singleton getInstance2(){
        return SingletonFactory.instance;
    }
}
